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United States Patent |
5,041,858
|
Yamamichi
,   et al.
|
August 20, 1991
|
Mount device
Abstract
A mount device for an interchangeable lens having a bayonet type mount
member capable, upon rotation relative to a mount member on a camera body,
of coupling with or decoupling from the latter, and a plurality of
electrical connection terminals arranged, upon completion of a coupling
operation of both mount members, to contact with the equal number of
electrical connection terminals on the camera body so that communication
become possible between the lens and the camera body. The axial rear ends
of the terminals on the lens project outwardly from the rear end surface
of the mount member on the lens and the rear end surface of the rearmost
lens.
Inventors:
|
Yamamichi; Masayoshi (Kanagawa, JP);
Fujino; Masahisa (Tokyo, JP)
|
Assignee:
|
Canon Kabushiki Kaisha (Tokyo, JP)
|
Appl. No.:
|
617375 |
Filed:
|
November 21, 1990 |
Foreign Application Priority Data
| Feb 17, 1986[JP] | 61-21417 |
| Feb 17, 1986[JP] | 61-21418 |
Current U.S. Class: |
396/532 |
Intern'l Class: |
G03B 017/14 |
Field of Search: |
354/286
|
References Cited
U.S. Patent Documents
3940777 | Feb., 1976 | Komine | 354/197.
|
4104649 | Aug., 1978 | Tanaka et al. | 354/286.
|
4448509 | May., 1984 | Katsuma et al. | 354/286.
|
4457609 | Jul., 1984 | Tomino et al. | 354/286.
|
4464034 | Aug., 1984 | Tomino | 354/286.
|
4527879 | Jul., 1985 | Hosoe et al. | 354/286.
|
4536071 | Aug., 1985 | Maekawa et al. | 354/400.
|
4596454 | Jun., 1986 | Kawai et al. | 354/286.
|
4603955 | Aug., 1986 | Haneishi | 354/286.
|
Foreign Patent Documents |
54-108628 | Aug., 1979 | JP.
| |
56-60911 | May., 1981 | JP.
| |
58-72132 | Apr., 1983 | JP.
| |
58-83824 | May., 1983 | JP.
| |
59-42527 | Mar., 1984 | JP.
| |
59-152424 | Aug., 1984 | JP.
| |
59-218412 | Dec., 1984 | JP.
| |
60-23841 | Feb., 1985 | JP.
| |
60-53912 | Mar., 1985 | JP.
| |
2078384 | Jan., 1982 | GB.
| |
2158957 | Nov., 1985 | GB.
| |
Other References
Rolleiflex SLX, Blueprints #566000412B1, (1974) and 5500143001 (Planar
28180) (1973).
Pliot Argus No. 83, Nov. 1977, "Le Rolleiflex SLX".
Photographic Industries, 2, '77, "Rolle; Relfex SLX", Feb. 1977.
Photographic Industries, 10, '82, "Mamiya RZ 67 Professional", Oct., 1982.
|
Primary Examiner: Gellner; Michael L.
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto
Parent Case Text
This application is a continuation of U.S. application Ser. No. 07/364,589
filed on June 12, 1989, which is a continuation of U.S. application Ser.
No. 07/253,921 filed on Oct. 6, 1988, which is a continuation of U.S.
application Ser. No. 07/014,021, filed on Feb. 12, 1987, all abandoned.
Claims
What is claimed is:
1. A bayonet-mount type optical accessory mountable on a camera body having
a plurality of electrically connecting terminals arranged around, but
below, an optical axis of the camera, a mirror which reflects light from
an object to a finder optical system, and a mount having a lock member and
a mount pawl thereon, wherein the optical accessory comprises:
a mount comprising a mount pawl engageable and disengageable by rotation
around the optical axis with the mount pawl of the camera body;
a plurality of electrically connecting terminals arranged to engage the
electrically connecting terminals of the camera body in the direction of
the optical axis when said mount of the optical accessory is rotated
around the optical axis to engage with the mount of the camera body so
that the plurality of electrically connecting terminals of the optical
accessory are located below the optical axis when the engagement of both
mounts is completed, and wherein connecting portions of said electrically
connecting terminals of the optical accessory are positioned behind said
mount pawl of the optical accessory in the direction of the optical axis,
said plurality of electrically connecting terminals being spaced from an
abutment surface of said optical accessory mount and said mount pawl
toward the optical axis and formed in a circumferential line with respect
to the optical axis;
said optical accessory mount including a receiving portion for receiving
the camera mount lock member upon completion of coupling between the
optical accessory connecting terminals and the camera body connecting
terminals, said receiving portion being located substantially 90.degree.
around the optical axis from a central portion of said optical accessory
connecting terminals;
a terminal base member formed in the shape of a circular arc and arranged
along the inner circumference of said optical accessory mount;
wherein said plurality of electrically connecting terminals of the optical
accessory are supported by said terminal base member, and wherein an end
portion of said terminal base member is located behind said mount pawl of
the optical accessory in the direction of the optical axis.
2. An optical accessory according to claim 1 wherein the camera further
comprises a rectangular mirror box, and wherein said electrically
connecting terminals of the optical accessory are, when the optical
accessory is engaged with the camera body, located outside of a
rectangular picture frame of the rectangular mirror box of the camera
body.
3. An optical accessory according to claim 1, wherein the optical accessory
comprises an interchangeable lens.
4. An optical accessory according to claim 1, wherein said plurality of
electrically connecting terminals of the optical accessory are fixed in
the optical accessory.
5. An optical accessory according to claim 1, wherein a rear corner of said
terminal base member has a tapered surface.
6. An optical accessory according to claim 1, wherein said end portion of
said terminal base member and said connecting portions of said optical
accessory electrically connecting terminals are aligned substantially in
the same plane.
7. An optical accessory according to claim 6, wherein a rear corner of said
terminal base member has a tapered surface.
8. An optical accessory according to claim 7, wherein said plurality of
electrically connecting terminals of the optical accessory are fixed in
the optical accessory.
9. A bayonet-mount type optical accessory mountable on a camera body having
a plurality of electrically connecting terminals arranged around, but
below, an optical axis of the camera, a mirror which reflects light from
an object to a finder optical system, and a mount having a lock member and
a mount pawl thereon, wherein the optical accessory comprises:
a mount comprising a mount pawl engageable and disengageable by rotation
around the optical axis with the mount pawl of the camera body;
a plurality of electrically connecting terminals arranged to engage the
electrically connecting terminals of the camera body in the direction of
the optical axis when said mount of the optical accessory rotates around
the optical axis to engage with the mount of the camera body so that the
plurality of electrically connecting terminals of the optical accessory
are located below the optical axis when the engagement of both mounts is
completed, and wherein connecting portions of said electrically connecting
terminals of the optical accessory are positioned behind said mount pawl
of the optical accessory in the direction of the optical axis, said
plurality of electrically connecting terminals being spaced from an
abutment surface of said optical accessory mount toward the optical axis
and formed in a circumferential line with respect to the optical axis;
said optical accessory mount including a receiving portion for receiving
the camera mount lock member upon completion of coupling between said
optical accessory electrically connecting terminals and said camera body
electrically connecting terminals, said receiving portion being located
substantially 90.degree. around the optical axis from a central portion of
said optical accessory connecting terminals, wherein said plurality of
electrically connecting terminals are disposed at a position such that
.theta.1 is greater than .theta.2, wherein .theta.1 is an angle between a
counterclockwise-most terminal when the optical accessory is mounted on
the camera and a point P at which a camera mirror box intersects an inner
curvature of the camera mount pawl, and where .theta.2 is an angle between
the counterclockwise-most terminal before the optical accessory is rotated
and after the optical accessory is rotated for mounting; and
a terminal base member, wherein said plurality of electrically connecting
terminals of the optical accessory are supported by said terminal base
member, and wherein an end portion of said terminal base member is located
behind said mount pawl of the optical accessory in the direction of the
optical axis.
10. A camera comprising:
a camera body having a plurality of electrically connecting terminals
arranged around, but below, an optical axis of the camera, and a mount
having a locking member and mount pawl thereon; and
a bayonet-mount type optical accessory mountable on said camera body,
wherein the camera comprises:
a mount having a mount pawl engageable and disengageable by rotation around
the optical axis with said mount pawl of said camera body;
a plurality of electrically connecting terminals arranged around, but
below, the optical axis of said camera to engage said electrically
connecting terminals of said camera body in the direction of the optical
axis when said mount of the optical accessory is rotated around the
optical axis to engage with said mount of said camera body so that said
plurality of electrically connecting terminals of said optical accessory
are located below the optical axis when the engagement of both mounts is
completed, and wherein connecting portions of said electrically connecting
terminals of said optical accessory are positioned behind said mount pawl
of the optical accessory in the direction of the optical axis, said
plurality of electrically connecting terminals of said optical accessory
being spaced from an abutment surface of said optical accessory mount and
said mount pawl of said optical accessory toward the optical axis and
formed in a circumferential line with respect to the optical axis;
said optical accessory mount including a receiving portion for receiving
said camera mount lock member upon completion of coupling between said
optical accessory connecting terminals and said camera body connecting
terminals, said receiving portion being located substantially 90.degree.
around the optical axis from a central portion of said optical accessory
connecting terminals;
a terminal base member formed in the shape of a circular arc and arranged
along the inner circumference of said optical accessory mount;
wherein said plurality of electrically connecting terminals of the optical
accessory are supported by said terminal base member, and wherein an end
portion of said terminal base member is located behind said mount pawl of
the optical accessory in the direction of the optical axis.
11. A camera according to claim 10 wherein said camera body further
comprises a rectangular mirror box, and wherein said electrically
connecting terminals of said optical accessory are, when said optical
accessory is engaged with said camera body, located outside of a
rectangular picture frame of said rectangular mirror box of said camera
body.
12. A camera according to claim 10, wherein said optical accessory
comprises an interchangeable lens.
13. A camera according to claim 10, wherein said plurality of electrically
connecting terminals of said optical accessory are fixed in said optical
accessory.
14. A camera according to claim 10, wherein a rear corner of said terminal
base member has a tapered surface.
15. A camera according to claim 10, wherein said end portion of said
terminal base member and said connecting portions of said optical
accessory electrically connecting terminals are aligned substantially in
the same plane.
16. A camera according to claim 15, wherein a rear corner of said terminal
base member has a tapered surface.
17. A camera according to claim 16, wherein said plurality of electrically
connecting terminals of said optical accessory are fixed in said optical
accessory.
18. A camera comprising:
a camera body having a mirror box, a plurality of electrically connecting
terminals, and a mount having a lock member and a mount pawl thereon; and
a bayonet-mount type optical accessory mountable on said camera body,
wherein the optical accessory comprises:
a mount comprising a mount pawl engageable and disengageable by rotation
around the optical axis with said mount pawl of said camera body;
a plurality of electrically connecting terminals arranged around, but
below, an optical axis of said camera to engage said electrically
connecting terminals of said camera body in the direction of the optical
axis when said mount of said optical accessory rotates around the optical
axis to engage with said mount of said camera body so that said plurality
of electrically connecting terminals of said optical accessory are located
below the optical axis when the engagement of both mounts is completed,
and wherein connecting portions of said electrically connecting terminals
of said optical accessory are positioned behind said mount pawl of said
optical accessory in the direction of the optical axis, said plurality of
electrically connecting terminals being spaced from an abutment surface of
said optical accessory mount toward the optical axis and formed in a
circumferential line with respect to the optical axis;
said optical accessory mount including a receiving portion for receiving
said camera mount lock member upon completion of coupling between said
optical accessory electrically connecting terminals and said camera body
electrically connecting terminals, said receiving portion being located
substantially 90.degree. around the optical axis from a central portion of
said optical accessory connecting terminals, wherein said plurality of
electrically connecting terminals are disposed at a position such that
.theta.1 is greater than .theta.2, wherein .theta.1 is an angle between a
counterclockwise-most terminal when said optical accessory is mounted on
said camera body and a point P at which said camera mirror box intersects
an inner curvature of the camera mount pawl, and where .theta.2 is an
angle between the counter-clockwise-most terminal before said optical
accessory is rotated and after said optical accessory is rotated for
mounting; and
a terminal base member, wherein said plurality of electrically connecting
terminals of said optical accessory are supported by said terminal base
member, and wherein an end portion of said terminal base member is located
behind said mount pawl of said optical accessory in the direction of the
optical axis.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a mount device in camera.
2. Description of the Related Art
As the means of releasably attaching a lens to a camera body, use is made
of the rotate-to-couple or -decouple type bayonet mount in which the
complete camera is set up or taken down by turning the camera body and the
lens at their respective coupling flanges clockwise or counter-clockwise
relative to each other.
In the vicinity of that mount there is a location member for determining
the angular position of the lens relative to the camera body at the end of
coupling with locking means therefor. Also provided are a wide variety of
members for transmitting or receiving mechanical signals and electrical
signals between the camera body and the lens, lens. For example the
driving power transmission is transmitted from the inside of the camera
body to the operating mechanism for the diaphragm in the lens barrel.
Also, the operative connections from a diaphragm position detector and a
full-open aperture sensor to the exposure control apparatus in the camera
body are arranged in highly concentrated relation. Hence, the narrow space
between the lens mount and the mirror box is filled with a very intricate
pattern of these members.
Moreover, in recent years, along with the development of cameras having an
ever higher degree of automation, the necessary number of members as such
is liable to further increase. As the additional members have to take
their places near the aforesaid transmission, the greater the number of
members arranged adjacent the lens mount, the poorer the compatibility
with the old types of lenses becomes. Even for assuring maintenance of
sufficient compatibility, the design of the lens mount and its peripheral
members is becoming more important.
Under such a situation, for, as the capabilities of the camera have
recently been broadened to include auto-focus with the necessity of
electrically transmitting and receiving much information between the
camera body and the lens, designers are planning to replace some of the
conventional mechanical connections by electrical connections with the
advantage of utilizing the interconnection terminals for the AF system in
common with those for the diaphragm control device or the like. This makes
more important the functions of the electrical interconnections. So, the
arrangement and construction of the terminals for the aforesaid
interconnections on the lens mount has come to largely affect the fidelity
of automation in the camera.
SUMMARY OF THE INVENTION
It is, therefore, an object of the invention to provide a mount device
which assures that when the lens is being attached to the camera body, all
of the many members arranged in the vicinity of the mount members can
never interfere with, or be damaged by, one another.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevational view from the front of the camera of an embodiment
of a mount on the camera body according to the present invention.
FIG. 2 is an elevational view from the back of the same camera of a mount
on the lens thereof.
FIG. 3 is a side sectional view of the same camera with its central portion
shown in detail.
FIG. 4 is a fragmentary sectional view of the same lens when it stands
alone with its mount on a desk, or the like.
FIG. 5 is a fragmentary sectional view in greatly exaggerated scale
illustrating the details of the location mechanism of FIG. 1.
FIG. 6 is a partly elevational partly sectional view of two sets of
connection terminals at an intermediate point during the rotation of the
lens relative to the camera body.
FIG. 7 is similar to FIG. 6 except that is shows the end of rotation of the
lens.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention is next described in connection with an embodiment
thereof by reference to the drawings.
The following embodiment is an example of application of the invention to
the camera having the rotate-to-couple or -decouple type bayonet mount in
which the mount on the lens is first placed into axial and angular
registry with the mount on the camera body and then turned to one
direction, or vice versa, when they are being coupled with, or decoupled
from, each other, respectively.
As shown in FIG. 1, the mount 1 on the camera body comprises an abutment
surface 1A of annular shape with its center at an optical axis O. Three
pawls 1C.sub.1, 1C.sub.2 and 1C.sub.3 are formed along the inner periphery
of the abutment surface 1A in equally spaced relation. FIG. 1 shows that
state of the mount 1 of the camera body which is looked from the front of
the camera. In this figure, a mount lock pin 2 is arranged in the abutment
surface 1A on the horizontal diagonal line at the center of the width of
the right hand side portion thereof. The tip of this pin 2 is urged to
project forwardly of the abutment surface 1A by a spring 24 positioned in
a proper recess of a wall member of a mirror box 4 as shown in FIG. 5.
When the coupling is complete, the pin 2 enters a detent oval groove 6
formed in a mount 5 on the lens. To decouple, the operator will push a
lock release button 25 against the bias force of a spring 26 toward the
front panel 22 of the camera housing. Such inward movement of the button
25 causes the mount lock pin 2 to be retracted from the abutment surface
1A (toward the above in FIG. 5) through a lever 23 which is fixedly
secured to the pin 2. Thus, the mount 5 is released from the locking. This
mount 5 also has an abutment surface 5A of the same annular shape as the
abutment surface 1A with its center at the optical axis O as shown in FIG.
2. Three pawls 5C.sub.1, 5C.sub.2 and 5C.sub.3 are formed along the inner
periphery of the abutment surface 5A in equally spaced relation and
arranged to engage with the pawls 1C.sub.1, 1C.sub.2 and 1C.sub.3 of the
mount 1 of the camera body respectively when they are rotated about the
optical axis O. FIG. 2 shows the completely coupled state of the mount 5
on the lens with the mount 1 on the camera body as viewed from behind the
rear end of the lens. In this figure, the detent groove 6 for the mount
lock pin 2 is cut in the abutment surface 5A on the horizontal diagonal
line at a point almost coincident with the center of the width of the left
hand (if viewed from the front of the camera, right hand) side portion
thereof.
Inwardly of the central one third of the lower half of each of the mounts 1
and 5 is projected a concentrically arcuate base plate 3 or 7
respectively, on which a plurality of, in this instance, seven, electrical
connection terminals 3A or 7A are arrayed in an arcuate row. These
terminals 3A and 7A are arranged to contact with each other in paired
relation when the coupling is complete. The functions of these paired
terminals 3A and 7A are to transmit or receive various electrical signals
between the circuitries of the camera body and the lens. For example,
electrical power from a battery in the camera body is supplied to the lens
therethrough, and information representing the F-number at full open
aperture and the focal length of the individual lens from a memory in the
form of ROM are brought into a central processing unit (CPU) in the camera
body therethrough.
In FIGS. 1 and 2, the base plates 3 and 7 carrying the respective sets of
terminals 3A and 7A are formed in a similar shape to each other, and their
sizes are limited to within the cross-section of a space between each
abutment surface 1A, 5A and the bottom plane of the mirror box 4 of
rectangular cross-section. This allows for easily assuring the admitting
of an effective light beam. Also, since, as shown in FIG. 3, an AF unit 18
(including light sensor and control circuits) usually occupies a space
between the mirror box and the bottom panel of the camera body 9, and
because it has deep connections with the terminals 3A, it is desirable to
use a flexible printed circuit board 19, which permits an electrical
connection therebetween to be easily established without having to
interfere with other members. It should be pointed out that in each of the
aforesaid sets of terminals 3A and 7A, the size of each terminal and the
distance between the adjacent two of the terminals are so determined that
when in coupling, the tolerances for the dimensions of the mounts do not
result in breaking the contact with each pair of terminals 3A and 7A, or a
cross-talk between the adjacent pairs of terminals.
Next referring to FIGS. 6 and 7, the structure of construction of each
terminal carrier is described.
FIG. 6 is a sectional view illustrating an intermediate operative position
of the mount device of the invention. Concerning the mount on the camera
body, all the seven terminals 3A.sub.1 to 3A.sub.7 are formed in a
pin-like similar shape to one another, and each has a semi-spherical head
and a collar at almost the center of the length thereof. The upper portion
above the collar is movably fitted in a hole formed in the base plate 3 of
electrically insulating material and the collar also in a over-bored hole.
Compression springs 3B.sub.1 to 3B.sub.7 between the respective collars of
the pins 3A.sub.1 to 3A.sub.7 and respective lead patches of the circuits
printed on the board 19 urge the terminals 3A.sub.1 to 3A.sub.7 to be
pushed upward as viewed in FIG. 6. As a result, the tips of the terminals
3A.sub.1 to 3A.sub.7 are projected outwardly of the outer surface of the
base plate 3 to a longer length than the distance between the base plates
3 and 7. For the lens, on the other hand, the terminals 7A.sub.1 to
7A.sub.7 of pin-like similar shape, each with a larger diameter portion at
the bottom end thereof, are buried in the electrically insulating base
plate 7. The tops of all the terminals 7A.sub.1 to 7A.sub.7 are
electrically connected to respective lead patches of circuits printed on a
flexible printed circuit board 21. Both leading and trailing end corners
of the terminal base plate 7 are cut off to form slant surfaces so that
the contact resistance against the terminals 3A.sub.1 to 3A.sub.7 is
reduced. When the lens side terminal base plate 7 moves in a direction
indicated by arrow A from the position of FIG. 6, the leading slant
surface pushes down the terminals 3A.sub.3 to 3A.sub.1 successively
against the springs 3B.sub.3 to 3B.sub.1, finally reaching the position of
FIG. 7 in which the coupling is complete. In this position, the upper and
lower terminals 7A.sub.1 to 7A.sub.7 and 3A.sub.1 to 3A.sub.7 in each pair
are axially aligned with each other to permit establishment of channels
for signal transmissions therebetween with high accuracy and reliability.
Since, at this time, the mount lock pin 2 engages in the detent groove 6
as has been described above, the once-established channels are maintained
against breaking or cross-talk.
In FIG. 3, the camera body 9 shown by a 2-dot-and-1-dash line contains a
main mirror 10 whose central portion is half-mirrored. The reflected light
beam L.sub.1 goes upward to a focusing screen 14 and therefrom through a
pentagonal roof type prism 15 to an eyepiece (not shown). Meanwhile, the
split-off light beam L2 is reflected by a submirror 12 downwardly past a
hole provided in the bottom of the mirror box 4 to the AF unit 18. The
main mirror 10 is supported on a bracket 11, and the submirror 12 on a
plate 13. The focusing screen 14 is mounted on a framework 16 and is
spaced apart from the prism 15 by a spacer 17.
It should be pointed out here that an annular ferrule having the pawls 5C
formed on the outer surface thereof and which also serves as a holder for
the rearmost lens member 8 protrudes rearwardly (toward the camera body 9
or a film plane) of a plane defined by the abutment surface 5A of the
mount 5 to a considerable length, and that the axially rear end face of
the terminal base plate 7, or the confront end surfaces of the terminals
7A, also protrudes rearwardly of a plane 5D defined by the rear end of the
annular ferrule to an appreciable length. When in the coupled position
shown in FIG. 3, the pawls 1C on the camera body side mount 1 and the
pawls 5C on the lens side mount 5 engage each other, and, at the same
time, the camera body side terminals 3A are in contact with the lens side
ones 7A. The lens barrel contains a circuit element assembly 20 including
a CPU having a ROM built therein. The circuit elements are connected to
the respective terminals 7A through a common flexible printed circuit
board 21. The length the terminal base plate 7 protrudes outwardly of the
plane 5D is so high that, as the rear vertex 8A of the lens lies inside
the plane 5D, even when the lens decoupled from the camera body slands on
the mount as shown in FIG. 4, the rear surface 8A of the lens will never
come into contact with the rough surface 27 of a desk or the like, thus
being protected from damages such as scratches. Further, since such
protrusion of the lens side terminals 7A permits the camera body side
terminals 3A to be positioned inwardly of a plane in which the pawls 5C
move when the lens is coupled with the camera body, there is no
possibility of the pawls 5c damaging the camera body side terminals 3A.
Returning to FIG. 1, another feature of the invention is described in
connection with the process for coupling the lens with the camera body.
The lens is first put on the camera body in axial alignment at such an
angular position that the lens side mount pawl 5C.sub.3 takes its place in
between the camera body side mount pawls 1C.sub.2 and 1C.sub.3 (the pawl
5C.sub.2 in between the pawls 1C.sub.1 and 1C.sub.2). In this state, the
lens side terminal base plate 7 is located at the starting end of
clockwise movement shown by a 2-dot-and-1-dash line. The distance between
the counter-clockwise-most electrical connection terminals 7A.sub.7 and
3A.sub.7 on the lens and the camera body subtends an angle .theta..sub.2
at the optical axis O (hereinafter called the "coupling" angle), while the
distance from a point P at which the line on the right hand side of the
mirror box 4 intersects the inner curvature of the pawl 1C.sub.1 to the
coupling start side terminal 3A.sub.7 subtends an angle .theta..sub.1.
With the help of this geometry, the invention sets forth a rule of design:
.theta..sub.1> .theta..sub.2. When this condition is satisfied, the
coupling rotation can be performed without suffering any mechanical
interference between the lens side terminal base plate 7 and the mirror
box 4 or the mirror 10, despite the projecting outwardly of the rear end
5D of the annular ferrule into the back space of a vertical plane falling
from the front side of the top wall of the mirror box 4. This makes it
possible to determine the maximum length of the mirror 10 by taking into
account only the rear end 5D of the annular ferrule and the rear vertex 8A
of the lens.
The above-described embodiment of the invention has the following
advantages:
(1) Because the confronting surfaces of the electrical connection terminals
between the lens and camera body are made axially positioned on the back
side of the rear end of the mount on the lens, there is no possibility of
occurrence of accidents such as the scratching of the electrical
connection terminals on the camera body by the mount pawl on the lens and
the electrical damage by abnormal contact.
(2) Even when the interchangeable lens slands alone on the ferrule, the
rearmost surface of the lens is not damaged, for the base plate carrying
the electrical connection terminals of the mount on the lens serves as a
protecting leg.
(3) Because the electrical connection terminals are arranged below the
bottom wall of the mirror box, it is easy to assure the full diameter of
the effective light beam. Also, since the AF unit that always necessitates
communications across the lens mount is usually installed on the bottom
panel of the camera housing, because the use of a flexible printed circuit
board is made to suffice for connecting the AF unit to the interconnection
terminals, it is easy to avoid any electrical interference between the AF
circuit and the other circuits. Further, this allows of creation of a
spare space, leading to increase the degree of freedom of the design of
the electrical connection terminals.
(4) Because the maximum acceptable range of rotation of the mount device is
so determined that when coupling, the electrical connection terminals of
the mount on the lens though projecting outwardly of the rear end of the
flange member thereof do not enter the path of movement of the front edge
of the mirror, the mirror can be designed in such a way that, while the
presence of the electrical connection terminals being neglected, only the
axial length of the annular ferrule and the rear vertex of the lens are
factored into the length of the mirror. This leads to minimize the
short-cut shade of the mirror.
(5) Because, differing from the conventional devices, it is in the upper
half of the mount device that there is no interconnection members between
the lens and the camera body, the focusing screen may be extended
frontward up to the rear end of the lens mount device. This leads to
facilitate an increase of the view area compared to the film area. If this
percentage is left unchanged from the conventional value, the flange back
can be made shorter than that when an interconnection member is arranged
in the space between the top wall of the mirror box and the flange member
of the mount device. Even for a case where use of the high relative
aperture lenses is considered, the diameter of the mount device can be
reduced. This leads to a more compact camera.
(6) Because there is no possibility of the occurrence of accidental contact
of the electrical connection terminals on the camera body with the
rearmost surface of the lens at any station during the coupling operation,
it is possible to design a lens of increased relative aperture in the form
that the clear-to-blank edge zone of the rearmost lens member is cut out
in a corresponding portion to the assembly of electrical connection
terminals. Hence, a lens of higher relative aperture with a shorter back
focal length can be designed in view of the more compact mount device.
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